Field of the Invention
This invention relates to a circuit and method for signal transmission, and in particular, it relates to signal transmission between different communication interfaces. It can support non-video and video signal transmission.
Description of Related Art
In the early days of computer systems, for connecting computers with external devices, a number of communication interfaces or connectors were used, such as PS/2 for mouse and keyboard, parallel ports (LPT port) for printers, RS233 for modems, etc. A problem with multiple kinds of interfaces is that driver programs must be installed, and they typically require a restart before use. These limitations are inconvenient to users. More recently, Universal Serial Bus (USB) is used to replace the above communication interfaces, which improves user friendliness and reduces incompatible communication interfaces. Today, USB is one of the commonly used communication interfaces.
USB is a serial interface bus standard used to connect computer systems and external peripheral devices, and as an input and output interface standard, it is widely used in connections between electronic devices, such as personal computers, mobile devices, digital TVs, printers, game devices, hard drives, etc., and they can have both data transmission and power supply functions. One major feature of USB is that it is hot-pluggable, i.e. it can be used as soon as it is plugged in. When the external device is connected to the computer via USB, the computer enumerates the external device, and load required driver programs, and communication can start without restarting the computer. With improvements in information technologies, the USB data transmission speed has increased. The transmission speed of only 1.5 Mbit/s for earlier USB 1.0 technologies had increased to 480 Mbit/s for USB 2.0 and 5 Gbps for USB 3.0, even up to 10 Gbps for USB 3.1. Common USB connectors are divided into A type and B type based on device requirements, and each type is further divided into micro and mini types. Based on USB 3.1 high speed transmission specification, the internal structure of Type C connectors can support high speed data transmission and power supply, as well as support Displayport. One feature of the exterior design of Type C connectors is that its upper and lower sides are identical, so the user does not need to distinguish between the “up” side and “down” side, and the connector can be plugged in with either side facing up.
With the advance of network technologies, Internet bas become an indispensable part of people's lives. The network brings convenience such as online shopping and communication across the ocean, etc. The large amount of data communication cannot be accomplished by individual servers, and multiple servers cooperating with each other are used to provide fast operations. To centrally manage servers, management personnel use KVM (keyboard, video, mouse) switches as control devices, which allows using one set of user terminal (keyboard, monitor, mouse) to control and manage multiple servers including their power supply and other settings. In addition, extenders are used to extend the signal transmission range, allowing remote control of servers, to improve space utilization efficiency.
Because Type-C USB connectors may potentially replace current Type-A and Type-B connectors, computers in the future may mainly used Type-C connectors. However, external devices using USB interface may still use current Type-A and Type-B connectors. Generally speaking, if an extender is to simultaneously support USB and Displayport devices, more connection lines need to be used to improve transmission speed, which increases cost. Take the example of extenders using fiber optic cables, USB signals need to be connected to 2 channels of optical transceiver module, Displayport high speed video signals require 2 or 4 channels of optical transceiver module, and the auxiliary channel (AUX) of Displayport also requires 2 channels of optical transceiver module.